Molecular layering of fluorinated ionic liquids at a charged sapphire (0001) surface.
Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of "green" applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.
Mezger
Markus
M
Max-Planck-Institut für Metallforschung, D-70569 Stuttgart, Germany.
Schröder
Heiko
H
Reichert
Harald
H
Schramm
Sebastian
S
Okasinski
John S
JS
Schöder
Sebastian
S
Honkimäki
Veijo
V
Deutsch
Moshe
M
Ocko
Benjamin M
BM
Ralston
John
J
Rohwerder
Michael
M
Stratmann
Martin
M
Dosch
Helmut
H